When Apple introduced the Apple Watch Series 8 on Wednesday, it launched a brand new low energy mode function that lets the wearable double its battery life by turning off a couple of options. It gained’t be restricted to Apple’s newest gadgets, although — during the presentation, Apple stated low energy mode is coming to “the Series 4 and later” with watchOS 9, which is launching September twelfth.

The firm didn’t say whether or not the mode could be as efficient on older gadgets because it claims will probably be on the Series 8 and Apple Watch Ultra (Apple says its greater watch will have the ability to go from 36 hours of runtime to 60 with the mode turned on). But primarily based on what we learn about the way it works, it’s clear that it’ll be much less efficient on at the least a couple of fashions.

Low energy mode conserves juice by turning off some options just like the always-on show, exercise autostart, coronary heart well being notifications, and extra, whereas retaining issues like exercise monitoring and fall detection switched on. While turning the display screen totally off will completely enhance battery life on a few of Apple’s watches, it gained’t do a lot for the Series 4, or both mannequin of the SE — they don’t have always-on shows to start with.

Apple didn’t reply to The Verge’s request for touch upon what varieties of options it’ll flip off on watches like the brand new SE, or whether or not the function is coming to the price range mannequin in any respect. The SE does match the outline of “Series 4 and later,” however low energy mode isn’t talked about on the SE’s product page.

Despite the caveats, it’s good to know that there’ll quickly be a option to eke out at the least a little bit extra runtime in your older watch, with out having to modify into the ultra-bare-bones power reserve mode, which solely shows the time while you press the watch’s facet button. That’s very true as these gadgets and their batteries become old — although it’s value noting that Apple will service watch batteries for $79 in the event you actually wish to make your Series 4 final so long as doable.